Marchiafava Bignami disease is defined by characteristic demyelination of the corpus callosum (erosion of the protective covering of nerve fibers joining the 2 hemispheres of the brain). The disease seems to most often affect severe and chronic alcoholics in their middle or late adult life. Early symptoms may include depression, paranoia, psychosis, or dementia. Seizures are common, and hemiparesis, aphasia, abnormal movements, and ataxia may sometimes progress to coma and/or death. The cause of Marchiafava Bignami disease, including the potential role of nutritional deficiency, remains unknown. Improvement and recovery of some individuals has been reported. Treatment focuses on nutritional support and rehabilitation from alcoholism.

Most individuals diagnosed with Marchiafava Bignami disease (MBD) have a history of alcoholism and poor nutrition. How onset occurs (suddenly or chronically) and the range of clinical symptoms vary among affected individuals. Generally, the most common presentation includes personality change and psychomotor impairment. Some individuals present to the hospital with sudden onset of stupor or coma, and some present with seizures. Other individuals may have acute, subacute, or chronic onset of dementia and/or gait problems. Psychiatric disturbances, incontinence, hemiparesis, aphasia, and apraxia have also been described.

In individuals who have recovered from Marchiafava Bignami disease (MBD), it is not clear whether improvement was a result of vitamin supplementation or merely a reflection of the disease's natural history. Treatment should generally focus on nutritional support and rehabilitation from alcoholism (when alcoholism is present). Various treatments, including those typically used for alcoholism in general, have been given to patients with MBD. Some have improved and some have not. The most common treatments are thiamine and other B vitamins (especially vitamin B-12 and folate, which is not a B vitamin but is commonly given with B-12). No specific proven treatment is available. It has been recommended that individuals who survive the disease receive rehabilitation and, if appropriate, alcohol and nutritional counseling.